Can an HDR movie from a 360 camera light a scene?
After a lot of experimentation, the answer is Yes, but the results aren't great, for a few reasons. I'm going to use HDR footage from the Insta360 ONE X for reference, not because it's particularly great at HDR movies, but it's pretty popular, and the results from other cameras in this price range (and higher) will be about the same.

1. Low dynamic range

360 HDR movies shot on action cams do yield High Dynamic Range movies, but we're talking about a pretty low end of 'High' here. Users of the popular HDRI resource HDRI Haven will be used to HDRIs with 15, sometimes 26 EV (Exposure Values) of dynamic range. This produces very accurate lighting results, delivering excellent shadow quality and color. The ONE X will get you 3 EV... 4 EV tops... delivering soft shadows and saturated lighting.

2. Low Resolution



This scene features an outdoor Insta360 ONE X frame from an HDR movie. (A disclaimer first: The yellow rectangle features some settings that I wouldn't recommend or consider good practice, but it does eke out better contrast in the scene to get more pronounced shadows.)

Even so, you can see that the background plate is pretty blurry. this is due to camera movement and because the equirectangular image is just 2880 x 1440 pixels - the native dimensions from the camera. And we're only seeing about a third of those pixels in the background - the other two-thirds are out-of-shot, wrapping around the rest of the 'World'.

3. Soft Shadows

The green circles point out the difference between the sharp, full-sun shadows in the footage, compared to the soft, indistinct shadows in the scene. There's also an excessive amount of blue coloration from the sky on the white plane. (Ignore the slight pink coloration under the ball; that's ambient light from my hand, holding the camera).

4. Shake

Ideally, each frame of an HDR movie has multiple bracketed shots from a single point in time and space. If the camera's moving, this isn't possible. In the shot above, I was walking under an arch. The blue circle indicates blurred building lines due to camera movement and shake. This shake also impacts dynamic range, due to a difference in camera position between when it took its low bracketed shot to its high bracketed shot of that frame. If the shots don't overlap exactly, lighting becomes indistinct and colors aren't computed accurately.

Summary

Live HDR footage can give you, quite literally, quick and dirty background plates. You can mitigate problems by using a stationary camera and low-contrast, cloudy days. If you need a motion background plate (driving scenes when people are in cars, for instance), the low-res background could be blurred, with in-scene constraints used to blur in the right directions, depending on camera angle.